Device for authorizing an unrestricted operating mode of a vehicle control device in the event of a failure of the ignition signal

ABSTRACT

A motor vehicle with an automated clutch in its drive train has a clutch control device for controlling the automated clutch and at least a further control device. The clutch control device and the further control device can be activated by means of an activation element which, when the ignition is switched on, sends an ignition signal V Z  to the clutch control device and to the further control device. The clutch control device is or remains activated if at least one of the ignition signal V Z  and an activity signal of the further control device is present.

BACKGROUND OF THE INVENTION

The invention relates to a motor vehicle with a plurality of controldevices that can be activated through an activation element. When theactivation element is in a switched-on condition, it emits an ignitionsignal V_(Z) to the control devices, and when the activation element isin a switched-off condition, it does not emit the ignition signal. Thecontrol devices, which are in signal communication with each other, areactivated by the ignition signal V_(Z) and deactivated by the absence ofthe ignition signal V_(Z).

In motor vehicles of the foregoing description, if the ignition signalfails to reach, e.g., only one of the control devices, this one controldevice is deactivated while the other control devices are or remainactivated. This can have the result that a blown fuse in the ignitioncircuit of a control device will cause the one control device to becomedeactivated although the ignition is not in the switched-off condition.The deactivated state of the one control device can affect the properfunctioning of the vehicle.

OBJECT OF THE INVENTION

The object of the invention is to provide a device that allows thefunctions of a motor vehicle to remain operable safely and substantiallywithout restriction even if the ignition signal V_(Z) fails to reach theinput of one of the control devices, as long as the same signal is stillbeing received by one or more of the other control devices.

As a further objective, the invention aims to provide a method by whichthe functions of a motor vehicle are kept operable safely andsubstantially without restriction even if the ignition signal V_(Z)fails to reach the input of one of the control devices, as long as thesame signal is still being received by one or more of the other controldevices.

SUMMARY OF THE INVENTION

To meet the foregoing objective, the invention provides the concept thatat least one of the control devices is designed so that it is notdeactivated by the absence of an ignition signal V_(Z), if the ignitionsignal V_(Z) is present in at least one other control device, or ifanother signal indicating the presence of an ignition signal exists atthe one control device. The presence of the ignition signal at the atleast one other control device is communicated through a signalconnection such as a data bus transmission to the control device thatfailed to receive the ignition signal. If for example the at least oneother control device is an engine control device that regulates therpm-rate of the engine, the presence of an rpm-signal from the engine,combined with the fact that the engine is running, can be taken as anindication that an ignition signal is present at the engine controldevice.

In a practical embodiment of the invention, if an ignition signal V_(Z)is received by the at least one other control device, the latter sends asignal through the signal connection or at least emits a signalindicating or representing the presence of an ignition signal.

Advantageous embodiments of the invention use the concept that thecontrol device is not deactivated in the absence of an ignition signalif a signal from at least one other control device is received thatindicates or represents the presence of an ignition signal.

It is likewise advantageous if a control device is allowed to sendsignals through the signal connection only if an ignition signal ispresent. This has the advantageous result that a control device willsend signals only if an ignition signal is present at that particularcontrol device. Thus, the presence of an ignition signal can be detectedalone by the fact that signals are being sent through the signalconnection. If a control device detects that signals are being sent fromanother control device, this means that the sending device is activatedand that it is receiving an ignition signal.

According to a practical concept of the present invention, controldevices in the activated condition send at least one signal through thesignal connection or emit at least one signal. It is further practical,if a control device that is not receiving an ignition signal sends adefined signal through the signal connection which indicates that anignition signal is not present at that particular control device.

According to a further concept of the invention it can be advantageousif at least two of the following control devices are provided in a motorvehicle and are in signal communication with each other:

a control device of a clutch with automated clutch-actuation;

a control device of an engine control;

a control device of a transmission control;

a control device of an anti-slip regulation;

a control device of an anti-lock braking system;

a control device of a traction control arrangement;

a control device of a climate control system;

a control device of a navigation system; or

another control device.

A further advantageous concept of the invention can be used in a motorvehicle that is equipped with an automated clutch, an engine, atransmission, a clutch control device for controlling the automatedclutch, and a unit for determining the rpm-rate n_(mot) of the engine,wherein the clutch control is normally activated by an activationelement which sends an ignition signal V_(Z) to the clutch controldevice when the ignition is switched on. According to the invention,even if the clutch control device fails to receive an ignition signal,it nevertheless remains activated as long as an engine rpm-signalindicates that the engine rpm-rate n_(mot) is above a predeterminedrpm-limit n_(limit).

The following concept of the invention can likewise be used to advantagein a motor vehicle that is equipped with an automated clutch, an engine,a transmission, a clutch control device for controlling the automatedclutch, and a further control device, wherein the clutch control deviceand the further control device are normally activated by an activationelement which sends an ignition signal V_(Z) to the control devices whenthe ignition is switched on. According to the invention, even if theclutch control device fails to receive an ignition signal, itnevertheless remains activated as long as the clutch control devicereceives a signal from the further control device indicating that anignition signal V_(Z) is present at the further control device.

Another advantageous concept within the scope of the invention can beused in a motor vehicle that is equipped with an automated clutch, anengine, a transmission, a clutch control device for controlling theautomated clutch, and a further control device, wherein the clutchcontrol device and the further control device are normally activated byan activation element which sends an ignition signal V_(Z) to thecontrol devices when the ignition is switched on. According to theinvention, even if the clutch control device fails to receive anignition signal, it nevertheless remains activated as long as the clutchcontrol device receives a signal from the further control deviceindicating that the further control device is in an activated state.

Yet another advantageous concept within the scope of the invention canbe used in a motor vehicle that is equipped with an automated clutch, anengine, a transmission, a clutch control device for controlling theautomated clutch, and a further control device, wherein the clutchcontrol device and the further control device are normally activated byan activation element which sends an ignition signal V_(Z) to thecontrol devices when the ignition is switched on. According to theinvention, even if the clutch control device fails to receive anignition signal V_(Z), it nevertheless remains activated as long as theclutch control device receives a signal from the further control deviceindicating that an ignition signal V_(Z) is present at the furthercontrol device and/or that the engine rpm-rate n_(mot) is above apredetermined rpm-limit n_(limit).

Yet another advantageous concept within the scope of the invention canbe used in a motor vehicle that is equipped with an automated clutch, anengine, a transmission, a clutch control device for controlling theautomated clutch, and a further control device, wherein the clutchcontrol device and the further control device are normally activated byan activation element which sends an ignition signal V_(Z) to thecontrol devices when the ignition is switched on. According to theinvention, even if the clutch control device fails to receive anignition signal V_(Z), it nevertheless remains activated as long as theclutch control device receives a signal from the further control deviceindicating that an ignition signal V_(Z) is present at the furthercontrol device and/or that the further control device is in an activatedstate.

Yet another advantageous concept within the scope of the invention canbe used in a motor vehicle that is equipped with an automated clutch, anengine, a transmission, a clutch control device for controlling theautomated clutch, and a further control device. According to the furtherinventive concept, at least the first control device, when in theactivated state, sends signals through a data bus.

A further advantageous concept within the scope of the invention can beused in a motor vehicle that is equipped with an automated clutch, anengine, a transmission, a clutch control device for controlling theautomated clutch, and a further control device. According to the furtherinventive concept, the first control device sends signals through a databus, if a signal is present that indicates that the further controldevice is in an activated state.

The following concept according to the invention can likewise be used ina motor vehicle that is equipped with an automated clutch, an engine, atransmission, a clutch control device for controlling the automatedclutch, and a further control device. According to the inventiveconcept, the first control device sends signals through a data bus if anengine-rpm signal is present indicating that an engine rpm-rate exceedsan rpm-limit.

Under a further advantageous concept of the invention, the first controldevice sends a starter release signal through the data bus when thetransmission is shifted into the neutral position.

It is likewise advantageous according to the invention, if the controldevice that controls the engine starts up the vehicle engine if astarter release signal is present and an engine-start operation isinitiated by the driver.

In the embodiments and concepts described herein, the control devicereferred to as “other” or “further” control device is advantageouslyrepresented by one of the following control devices:

a control device of an engine control;

a control device of a transmission control;

a control device of an anti-slip regulation;

a control device of an anti-lock braking system;

a control device of a traction control arrangement;

a control device of a climate control system;

a control device of a navigation system; or

another control device.

It is likewise advantageous if at least one control device is anelectronic control device with a microprocessor.

It is further advantageous if the signal connection is a data busconnection. It is particularly useful if the signal connection is aCAN-bus (Central Area Network bus) connection.

It is further practical if at least one of the following elements isused as activation element:

an ignition switch for switching on the ignition of the vehicle;

a vehicle brake operating element, such as a pedal and/or handle;

a transponder code card.

It is further practical if, prior to its deactivation, the controldevice of the automated clutch moves the clutch into engagement, whichhas the effect of a parking lock if the transmission is in gear. It islikewise advantageous if a variable predeterminable length of time liesbetween the engagement of the clutch and the deactivation of the controldevice. The length of the time interval can be a function of vehicleparameters.

It is likewise practical if the at least one signal which indicates orrepresents the presence of an ignition signal is constituted by one ofthe following signals:

an ignition signal V_(Z)

an activity signal of a control device

an engine rpm-rate signal n_(mot)

a throttle valve signal

a fuel-injection rate signal

an engine torque signal M_(mot)

a wheel rpm-rate signal n_(wheel)

a transmission rpm-rate signal n_(trsm).

A further concept of the invention relates to a method for controllingsubsystems in the drive train of a motor vehicle such as an automatedclutch, with at least one control device for controlling the operationof the automated clutch and at least one other control device whereinthe control devices are activated when a switching element is switchedon and deactivated when the switching element is switched off. Theinventive method includes at least some of the following steps:

interrogating whether an ignition signal or an engine rpm-rate signal ispresent at the at least one control device;

leaving the control device activated if at least one of the two signalsis present;

emitting no signals from the control unit through a data bus if neitherof the two signals is present;

deactivating the control unit if neither of the two signals is present.

A further embodiment of the foregoing inventive method, likewise,relates to the control of subsystems in the drive train of a motorvehicle such as an automated clutch, with at least one control devicefor controlling the operation of the automated clutch and at least oneother control device wherein the control devices are activated when aswitching element is switched on and deactivated when the switchingelement is switched off. The inventive method includes at least some ofthe following steps:

interrogating whether an ignition signal, engine rpm-rate signal and/orand engine control activity signal is present at the at least onecontrol device;

leaving the control device activated if at least one of the ignitionsignal, the engine rpm-rate signal, or the engine activity signal ispresent;

emitting no signals from the control unit through a data bus in theabsence of the ignition signal if neither the engine rpm-rate signal northe engine activity signal is present;

deactivating the control unit in the absence of the ignition signal ifneither the engine rpm-rate signal nor the engine activity signal ispresent.

In a practical embodiment of the invention, the control device is acontrol device for controlling the automated clutch. Prior todeactivation of the control device the clutch is moved into engagement.

It is likewise advantageous if a waiting time is observed prior to thedeactivation of the control device. It is particularly advantageous if awaiting time is observed prior to the engagement of the clutch. Thelength of either of the waiting periods can be dependent on at least oneoperating parameter of the vehicle.

The device according to the invention ensures that a safe operation ofthe automated clutch is maintained if the ignition signal fails to bereceived at the input of the control device of the automated clutch. Afurther embodiment ensures a safe switching-on or restarting of theengine after it has been switched off even if at least the controldevice of the automated clutch is not receiving the ignition signal.

The invention further relates to a motor vehicle with a plurality ofcontrol devices which are activated through an activation element whichsends out an ignition signal V_(Z), wherein the control devices are insignal connection with each other and mutually monitor each other,wherein at least one control device is not caused to be deactivated bythe absence of an ignition signal V_(Z) as long as an ignition signalV_(Z) is present in at least another control device or if the at leastone control device is receiving another signal indicating the presenceof an ignition signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be explained below in further detailwith reference to the drawings, wherein:

FIG. 1 shows a diagrammatic illustration of a motor vehicle;

FIG. 2 represents a block diagram;

FIG. 3 represents a flowchart;

FIG. 4 represents a flowchart;

FIG. 5 represents a flowchart;

FIG. 6 represents a flowchart; and

FIG. 7 represents a flowchart.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a motor vehicle 1 with a drive source 2 such as aninternal combustion engine or a hybrid combination of an internalcombustion engine and an electric motor. In the drive train of the motorvehicle, the drive source 2 is followed by a clutch 3, a transmission 4,a drive shaft 5, and a differential 6 driving two drive shafts 7 a and 7b which, in turn, drive the driven wheels 8 a and 8 b. The clutch 3 isrepresented by a dry friction clutch that is mounted on a flywheel, witha pressure plate 10, clutch disc release bearing 12 and release fork 13.The release fork is actuated by means of an actuator 15 with a mastercylinder 16, a pressure-medium conduit such as a hydraulic line 17, anda slave cylinder 18. The actuator is provided with a snifting channel 21that is connected to a reservoir 22 for the pressurized medium. Theactuator is configured as a pressure medium-based actuator with anelectric motor 19 driving the master cylinder piston 20 through agearbox so that the torque transfer through the clutch can be controlledthrough the pressurized medium conduit 17 and the slave cylinder 18.

Furthermore the actuator 15 comprises a control device with anelectronic control unit for controlling or regulating the operation ofthe clutch by means of the actuator. The power electronics and/or thecontrol electronics can be accommodated inside the actuator housing, butthey could also have their own separate housings.

The vehicle 1 with transmission 4 has a gear shift lever 30 with agear-identification sensor 31 and/or shift-intent sensor 32 mounted onthe transmission or on the shift lever. The gear-identification sensorserves to detect which gear is engaged, while the shift-intent sensordetects conditions that indicate a driver's intention to shift gears,which manifests itself through a movement of the shift lever and/or aforce exerted on the shift lever. The vehicle is further equipped withan rpm-sensor 33 which detects the rpm-rate of the transmission outputshaft or the driven wheels. A throttle valve sensor 34 detects theposition of the throttle valve, and an rpm-sensor 35 detects the enginerpm-rate.

The gear-identification sensor directly or indirectly detects theposition of shift elements inside the transmission, or it detects whichgear is engaged in the transmission so that based on the sensor signal,at least the currently engaged gear is registered by the control unit.Furthermore, if the sensor is based on an analog principle, the movementof the shift elements inside the transmission can be detected so thatthe next gear that is about to be engaged can be identified early.

The actuator 15 is supplied by a battery 40 that has a permanentconnection 42 b with the actuator. By connecting the battery to theactuator 15 through the ignition switch 41, the control unit isactivated and the microcomputer of the control unit is put intooperation. An ignition signal V_(Z) indicating that the ignition switchis in the “ON” position is present at the ignition input of the controlunit 15. As a rule, the ignition lock device has a multi-stage ignitionswitch 41 that is operated by means of the ignition key. In a firstposition of the switch, the control unit is activated by the presence ofthe ignition signal V_(Z), and in a second position of the switch astarter of the combustion engine 2 can be switched on by way of theelectronic engine control unit 50 to start up the engine.

When the ignition switch 41 is turned off, all of the control devices ofthe automated clutch, the engine and other units, if there are any, areswitched off as there is no longer an ignition signal present at thecontrol devices.

The control devices 15 and 50 are connected to the power supply 40through the permanent connections 42 a, 42 b and the switchableconnections 43 a, 43 b. The control devices are activated when theswitch 41 is closed, so that an ignition signal V_(Z) is received by thecontrol devices.

As a rule, there are fuses arranged in the circuit between the ignitionswitch and the control devices to protect the power-consuming devices.The fuses are symbolically indicated at 103, 105, 107, 109 in FIG. 2.

A data bus connection 60, such as for example a CAN-bus, is arrangedbetween the individual control devices of the motor vehicle. The controldevices send and/or receive signals through the data bus, such ascontrol commands, status signals, or sensor data. For example, theengine control unit can detect the engine rpm-rate and share theinformation through the data bus with the other control devices so thatthe same data do not have to be determined again by the other controldevices.

The block diagram 100 of FIG. 2 illustrates the overall circuitstructure of the control devices. The control devices are switched on byan ignition switch 101 in the position “Ignition on” and switched off inthe position “Off”. If the ignition switch is switched through theposition “Ignition on” into the “engine start” position, the engine isstarted up by the starter. The control devices of the automated clutchcontrol 102, the engine control 104, the ABS-control 106 (anti-lockbraking system) and other control devices 108 are shown as examples ofcontrol devices. Each of the control devices is connected through a fuse(103, 105, 107, 109) to the ignition switch so that the individualdevices are electrically protected. Furthermore, the control devicescommunicate through the data bus 110 with each other and send andreceive data and signals through the data bus.

If one of the fuses 103 to 109 fails, the respective control devicereceives the same signal or absence of a signal as if the ignition hadnot been switched on or had been switched off again.

The invention proposes an arrangement where, e.g., if the fuse 103 ofthe clutch control device 102 fails during operation of the vehicle sothat the control device no longer receives the ignition signal V_(Z),the control device 102 will recognize that the signal interruption wasnot caused by turning off the ignition but is due to another cause, suchas for example a malfunction.

The foregoing concept can be realized, e.g., by using the fact that atleast some of the individual control devices communicate through a databus, such as a CAN-bus and that despite the failure or absence of theignition signal V_(Z) at the clutch-control device 102, the othercontrol devices are still operating and continue to send and/or receivedata through the data bus. For example, the engine rpm-rate regulated bythe engine control 104 can be detected or received through the data busand interpreted as an indication that an ignition signal V_(Z) ispresent at the other control devices.

Another example of a signal that can serve as an indication for thepresence of an ignition signal V_(Z) is the wheel rpm-signal of the ABScontrol device.

Furthermore, the data bus signals of the different devices can bemonitored since the control devices send data through the data bustogether with a device identification. If no ignition signal V_(Z)exists at one of the control devices, the latter can cease sending datathrough the data bus, but the data traffic from the other controldevices on the data bus can continue. If, e.g., one control device isnot sending data, this can be interpreted by other control devices as anindication that no ignition signal V_(Z) exists at the silent controldevice.

An ignition signal V_(Z) is received by a control device if the ignitionis switched on and the electrical connection to the control device isnot interrupted. As described above, an interruption can be caused by ablown fuse and/or by another fault such as for example a break in thecable.

The flowchart 200 of FIG. 3 illustrates the sequence of operationsperformed by an embodiment of a device according to the invention and atthe same time illustrates an embodiment of a method according to theinvention.

The process starts in step 201 and repeats itself with each clock cycleof the control, for example every 10 ms. In step 202 the control deviceof the automated clutch performs a yes/no test on whether or not theengine control device is sending data to the data bus, e.g., to aCAN-bus. In the affirmative case, i.e., if signals of the engine controlunit are present on the data bus, the process continues at step 203,otherwise the process continues at step 207.

In one embodiment, the yes/no decision in step 202 can be independent ofthe nature of the data being sent by the engine control unit.

In another embodiment of the invention, if data are being sent by theengine control unit but all data are equal to zero in each successivecycle of the process, this is interpreted as an indication that theengine control unit is inactive, i.e., a negative outcome of step 202.

In the affirmative case of step 202, the engine control activity bitB_MOT_AKTIV in the control device is set to 1 in step 203 of theprocess.

Step 204 represents another yes/no decision on whether the enginerpm-rate exceeds a limit of, e.g., 200 rpm. The affirmative case meansthat the engine is running. In step 205, the bit B_MOT_RUNNING istherefore set to 1. The negative case of step 204 is interpreted as anon-running state of the engine; the process continues in step 206,where the bit B_MOT_RUNNING is set to 0.

In the negative case of step 202, the process continues in step 207where the bit B_MOT_AKTIV is set to zero, continuing with step 208 wherethe bit B_MOT_RUNNING is likewise set to zero. In this state, the enginecontrol is inactive, and the engine is either not running at all or isrunning slower than the limit of 200 rpm. The 200 rpm limit is givenonly as an example of a limit in the range from 100 rpm to 500 rpm,i.e., an rpm-rate that is clearly below the idling rate of the engine.

Step 209 represents a test as to whether the ignition signal V_(Z) from,e.g., the ignition switch is present at the control unit 102 or whetherthe bit B_MOT_RUNNING=1 is set. If either one or both of theseconditions are present (affirmative), the operating state of theignition is interpreted as “ON” in step 210. If neither of theconditions is present in step 209 (negative case), the operating stateof the ignition is interpreted as “OFF” in step 211. In step 212, if theignition has been found to be “ON”, the control device follows a programroutine or strategy for normal driving operation. This means, e.g., whentaking off from a stand-still, the clutch is moved into engagement; inpreparation for a gear change the clutch is disengaged; after completingthe gear change the clutch is re-engaged; or when the vehicle is slowingdown to a stop the clutch is taken out of engagement. Also in step 212,but in the case where the ignition has been found to be “OFF”, theclutch is put into engagement so that with a gear engaged in thetransmission, the vehicle is effectively secured in a parking-lockcondition and thereby prevented from unintentionally rolling away.Further process steps (not shown) in the control sequence of the clutchoperation follow after 213.

The flowchart 250 of FIG. 4 illustrates the sequence of operationsperformed by an embodiment of a device according to the invention and atthe same time illustrates an embodiment of a method according to theinvention.

The process starts in step 251 and repeats itself with each clock cycleof the control, for example every 10 ms. In step 252 the control deviceof the automated clutch performs a yes/no test on whether or not theengine control device is sending data to the data bus, e.g., to aCAN-bus. In the affirmative case, i.e., if signals of the engine controlunit are present on the data bus, the process continues at step 253,otherwise the process continues at step 254.

In the affirmative case of step 252, the engine control activity bitB_MOT_AKTIV in the control device is set to 1 in step 253 of theprocess.

In the negative case of step 252, the process continues in step 254where the bit B_MOT_AKTIV is set to zero. In this state, the enginecontrol is inactive.

Step 255 represents a test as to whether the ignition signal V_(Z) from,e.g., the ignition switch is present at the control unit 102 or whetherthe bit B_MOT_RUNNING=1 is set. If either one or both of theseconditions are present (affirmative), the operating state of theignition is interpreted as “ON” in step 256. If neither of theconditions is present in step 255 (negative case), the operating stateof the ignition is interpreted as “OFF” in step 257. In step 258, if theignition has been found to be “ON”, the control device follows a programroutine or strategy for normal driving operation. This means, e.g., whentaking off from a stand-still the clutch is moved into engagement; inpreparation for a gear change the clutch is disengaged; after completingthe gear change the clutch is re-engaged; or when the vehicle is slowingdown to a stop the clutch is taken out of engagement. Also in step 258,but in the case where the ignition has been found to be “OFF”, theclutch is put into engagement so that with a gear engaged in thetransmission, the vehicle is effectively secured in a parking-lockcondition and thereby prevented from unintentionally rolling away.Further process steps (not shown) in the control sequence of the clutchoperation follow after 259.

The flowcharts 300 and 350 of FIGS. 5 and 6, respectively, illustratesequences of operations performed by embodiments of a device accordingto the invention and at the same time illustrate embodiments of methodsaccording to the invention.

In step 301 of FIG. 5, the respective processes whose description wasended at step 213 of FIG. 3 or step 259 of FIG. 4 are continued. Step302 represents a test as to whether the ignition signal V_(Z) is presentand/or whether the bit B_MOT_RUNNING=1 is set. In the affirmative caseof step 302, the control device of the automated clutch sends signals tothe data bus (CAN bus) in step 303. Subsequently in step 304, thecontrol device releases the starter, e.g., under the conditions that thetransmission is in the neutral position and the engine is not running.The starter release signal is sent through the CAN-bus. After the enginecontrol device receives the starter release signal and the driver turnsthe ignition key to the engine start position, the engine is started instep 305. In the negative case of step 302, the process passes to step306 where the control device of the automated clutch is blocked fromsending signals to the data bus. In step 307, the control unit sends nostarter release signal, even if the transmission is in neutral and theengine is not running. If a starter release signal is set, the enginecontrol unit does not receive it, because it is not being sent, and theengine is therefore not being started even if the ignition key is turnedinto the engine start position by the driver in step 308. At step 309the process continues through further steps that are not shown in FIG.5.

In step 351 of FIG. 6, the respective processes whose description wasended at step 213 of FIG. 3 or step 259 of FIG. 4 are continued. Step352 represents a test as to whether the ignition signal V_(Z) is presentand/or whether the bit B_MOT_AKTIV=1 is set. In the affirmative case ofstep 352, the control device of the automated clutch sends signals tothe data bus (CAN-bus) in step 353. Subsequently in step 354, thecontrol device releases the starter, e.g., under the conditions that thetransmission is in the neutral position and the engine is not running.The starter release signal is sent through the CAN-bus. After the enginecontrol receives the starter release signal and the driver turns theignition key to the engine start position, the engine is started in step355. In the negative case of step 352, the process passes to step 356where the control device of the automated clutch is sending signals tothe data bus. In step 357, the starter release signal is set to theblocked condition, even if the transmission is in neutral and the engineis not running. Without the starter release signal, the engine will notstart even if the ignition key is turned into the engine start positionby the driver in step 358. At step 359 the process continues throughfurther steps that are not shown in FIG. 6.

The embodiments of FIGS. 5 and 6 have the advantage that the driver canstart the engine and put the vehicle in motion even if there is noignition signal V_(Z) present at one of the control devices after theignition has been switched on. Without the benefit of the inventivearrangement, the driver would in the event of a failure, for example inan electric cable or a fuse, no longer be able to start up the engineand the vehicle would be inoperative as a result of the failure.

A presence of a fault can be detected from the fact that the ignitionsignal V_(Z) is absent only at one control device but is present in atleast one other control device or all other control devices. If thecontrol devices are connected through a signal connection such as a databus and data and signals are exchanged through the data bus, the controldevice that lacks the ignition signal recognizes that the ignitionsignal is present at the other control devices, because they are sendingsignals to the data bus. In this situation the activity of the controldevice that lacks the ignition signal is carried out so that as long asignition signals are present at the other control devices, the absenceof the ignition signal is ignored and instead the activity of the othercontrol devices sending signals over the data bus is taken as anindication for the presence of an ignition signal. If the ignition isactually switched off by the driver, none of the control devices issending data over the data bus. Based on the absence of datacommunication on the data bus, the control devices will identify ageneral absence of an ignition signal and turn themselves offautomatically. The switch-off can also occur with a time delay duringwhich the control devices continue to check whether data are sent to thebus. In another embodiment, a control device does not cease to send datato the data bus in order to indicate the absence of an ignition signal,but instead sends predefined signals such as, e.g., zeroes which carrythe meaning of that no ignition signal is present at the control device.

With some embodiments, an operating phase of the motor vehicle that wasstarted while an ignition signal was present can be completed after thefailure of the ignition signal of the control device of the automatedclutch while full driving functionality is maintained. Under thisconcept, a CAN signal IDxxx, e.g., as an identifier of the enginecontrol device, is monitored in addition to the ignition signal of theautomated clutch. As long as the engine control device sends an enginerpm-rate greater than for example 210 rpm along with the IDxxx signal,the control device of the automated clutch maintains the normal workingmode even in the absence of an ignition signal. The failure of theignition signal at the control device of the automated clutch isindicated to the driver of the vehicle for example through a signal inthe instrument panel of the vehicle or by a failure of the gearindicator which indicates the currently engaged gear. The control deviceof the automated clutch sends signals through a signal connection suchas the CAN bus only when the ignition signal is present at the clutchcontrol device.

For example, if there is no ignition signal at the input of the controldevice of the automated clutch during 5 successive interrupts (e.g.,10-millisecond cycles) of the control device of the automated clutch andthe engine control device sends, e.g., an engine rpm-signal of less than210 rpm for three 20-millisecond cycles of the engine control, thecontrol device of the automated clutch may be programmed to recognizethe condition “ignition OFF”. At this point, a predefined “parking lock”function is activated and the clutch is moved into engagement.

After a run-out period that depends on the engine rpm-rate, the controldevice of the automated clutch switches off completely. A new start ofthe engine after a failure of the ignition signal is not possible withthe preceding embodiment.

Under the foregoing strategy, the control of the automated clutch issubstantially dependent on the engine rpm-signal during the shut-downperiod of the engine control device, i.e., after “ignition OFF”. As longas the engine control sends an rpm-signal greater than a threshold valuein the range of 100 to 500 rpm, for example 210 rpm, the control deviceof the automated clutch detects an “ignition ON” even though no ignitionsignal is present at the clutch-control device. Therefore, theclutch-control device keeps the automated clutch operative during theshut-down period of the engine-control device.

The invention provides the following concepts for signals to be sent bythe engine control device after receiving an “ignition OFF” signal:

1. The engine control device sends no signals on the CAN bus after“ignition OFF”. The control device of the automated clutch recognizesthe state “ignition OFF” as soon as the ignition is actually switchedoff. The run-out time of the engine—i.e., the delay time for engagingthe clutch under the parking-lock function—is calculated from the enginerpm-signal last sent prior to “ignition OFF”, such as for example 850rpm. The clutch control device is programmed to apply the correct amountof delay time compatible with this last rpm-signal.

2. The engine control device sends an rpm-signal of 0 rpm during theshut-down period. The control device of the automated clutch recognizesimmediately after the “ignition OFF” signal that the ignition switch hasbeen turned off and activates the parking lock by engaging the clutchwith a time delay. The run-out time period of the engine is calculatedfrom the last rpm-rate of the engine prior to switching off theignition, e.g. 850 rpm. The clutch control device is programmed to applya safe amount of delay time compatible with this last rpm-signal.

3. The engine control device sends the actual rpm-rate during therun-out period. The control device of the automated clutch does notrecognize the “ignition OFF” condition until the engine rpm-rate hasfallen below the limit of, e.g., 210 rpm. The run-out time period of theengine is calculated from the last rpm-rate before passing through the210 rpm threshold, e.g. 211 rpm. The clutch control device is programmedto apply a safe amount of delay time compatible with this lastrpm-signal.

FIG. 7 represents a flowchart diagram to illustrate an embodiment of theinvention. Step 401 represents a test as to whether the engine rpm-raten_Motor is greater than a predetermined limit, in this case 210 rpm. Inthe affirmative case of step 401, a substitute ignition signal such asbit flag “ON” is set at 402. In the negative case of step 401, thesubstitute ignition signal is set to “OFF” at step 403. Step 404represents a test as to whether the ignition signal or the replacementsignal is set to “ON”. In the affirmative case of step 404, theoperating state of the ignition is registered as “ON” in step 405. Inthe negative case of step 404, the operating state of the ignition isregistered as “OFF” in step 406. In block 407 the currently applicableoperating strategy is carried out. If the ignition flag is set to “ON”,the control strategy for driving, shifting, starting off, coasting,braking and stopping, etc., is carried out, and the shift-intentdetection is operative. If the ignition flag is set to “OFF”, the clutchis engaged after a predetermined time delay to immobilize the vehicle ina parking-lock condition. The shift-intent detection is deactivated,which means that the clutch does not move out of engagement when theshift lever is actuated. Step 408, represents one more test of theignition signal. If the ignition signal is “ON”, the control device ofthe automated clutch sends signals on the CAN bus in step 409. In thenegative case of step 408, the control device of the automated clutch isblocked from sending signals in step 410, which means that the starteris not released to start the engine.

FIG. 2

101 Ignition

102 AK control (automatic clutch control)

104 Engine control

106 ABS control

108 Other control devices

FIG. 3

202 Engine control emitting?

204 Engine speed >200 1/min

209 Ignition signal or B_MOT_DREHT=1

210 Ignition=ON

211 Ignition=OFF

212 If ignition=ON: normal driving state

If ignition=OFF: Parking lock

Ja/Nein Yes/no

FIG. 4

252 Engine control emitting?

255 Ignition signal or B_MOT_AKTIV=1

256 Ignition=ON

257 Ignition=OFF

258 If ignition=ON : Normal driving state

If ignition=OFF Parking lock

Ja/Nein Yes/no

FIG. 5

302 Ignition signal or B_MOT_DREHT 1

303 AK control emitting

304 Starter release

305 Engine start

306 AK not emitting

307 No starter release

308 No engine start

FIG. 6

352 Ignition signal or B_MOT_AKTIV=1

353 AK control emitting

354 Starter release

355 Engine start

356 AK not emitting

357 No starter release

358 No engine start

FIG. 7

402 Replacement ignition signal=ON

403 Replacement ignition signal OFF

404 Ignition signal=ON or

Replacement ignition signal ON

405 Ignition ON

406 Ignition=OFF

407 Sequence:

Ignition=ON: Driving, coasting (SA active)

Ignition=OFF: Parking lock (SA not active)

408 Ignition signal=ON

409 AK emitting on CAN

410 AK NOT emitting on CAN (no starter release)

What is claimed is:
 1. A motor vehicle with a drive train comprising anengine, a transmission, and an automated clutch, with a clutch controldevice for controlling the automated clutch and with a unit fordetermining an engine rpm-rate n_(mot), wherein the clutch controldevice is activated by means of an activation element which, when theignition is switched on, sends an ignition signal V_(Z) to the clutchcontrol device, and wherein in the absence of the ignition signal at theclutch control device, the clutch control device remains activated if anengine rpm signal n_(mot) which lies above a predetermined rpm-limitn_(limit) is present at the clutch control device.
 2. A motor vehiclewith a drive train comprising an engine, a transmission, and anautomated clutch, with a clutch control device for controlling theautomated clutch and with at least a further control device, wherein atleast the clutch control device and the further control device areactivated by means of an activation element which, when the ignition isswitched on, sends an ignition signal V_(Z) to the clutch controldevice, and wherein in the absence of the ignition signal at the clutchcontrol device, the clutch control device remains activated if theclutch control device receives from the further control device a signalindicating that the ignition signal V_(Z) is present at the furthercontrol device.
 3. A motor vehicle with a drive train comprising anengine, a transmission, and an automated clutch, with a clutch controldevice for controlling the automated clutch and with at least a furthercontrol device, wherein at least the clutch control device and thefurther control device are activated by means of an activation elementwhich, when the ignition is switched on, sends an ignition signal V_(Z)to the clutch control device, and wherein in the absence of the ignitionsignal at the clutch control device, the clutch control device is orremains activated if at the clutch control device there is a signal fromthe further control device which indicates an activation of the furthercontrol device.
 4. A motor vehicle with a drive train comprising anengine, a transmission, and an automated clutch, with a clutch controldevice for controlling the automated clutch and with at least a furthercontrol device, wherein at least the clutch control device and thefurther control device are activated by means of an activation elementwhich, when the ignition is switched on, sends an ignition signal V_(Z)to at least the clutch control device and to the further control device,and wherein the clutch control device is or remains activated in thepresence of at least one of the ignition signal V_(Z) and an enginerpm-signal indicating an engine rpm-rate n_(mot) above an rpm-limitn_(limit).
 5. A motor vehicle with a drive train comprising an engine, atransmission, and an automated clutch, with a clutch control device forcontrolling the automated clutch and with at least a further controldevice, wherein at least the clutch control device and the furthercontrol device are activated by means of an activation element which,when the ignition is switched on, sends an ignition signal V_(Z) to atleast the clutch control device and to the further control device, andwherein the clutch control device is or remains activated in thepresence of at least one of the ignition signal V_(Z) and an activitysignal of the further control device.
 6. The motor vehicle according toclaim 5, wherein at least the clutch control device in the activatedstate sends signals through a data bus.
 7. The motor vehicle accordingto claim 5, wherein at least the clutch control device with the presenceof said activity signal of said further control device sends signalsthrough a data bus.
 8. The motor vehicle according to claim 5, whereinat least the clutch control device with the presence of an enginerpm-signal indicating an engine rpm-rate above an rpm-limit sendssignals through a data bus.
 9. The motor vehicle according to claim 6,wherein the clutch control device, when neutral is engaged in thetransmission, sends a starter release signal through the data bus. 10.The motor vehicle according to claim 9 wherein the at least one furthercontrol device comprises an engine control device, and wherein saidengine control device starts up the vehicle engine with the presence ofthe starter release signal and an engine start operation initiated bythe driver.
 11. The motor vehicle according to claim 5, wherein thefurther control device comprises one of: a control device of an enginecontrol; a control device of a transmission control; a control device ofan anti-slip regulation; a control device of an anti-lock brakingsystem; a control device of a traction control regulator; a controldevice of a climate control system; a control device of a navigationsystem; and a control device of an anti-slip regulation.
 12. The motorvehicle according to claim 5, wherein the further control device is anelectronic control device with a microprocessor.
 13. The motor vehicleaccording to claim 5, wherein the activity signal is transmitted on adata bus connection.
 14. The motor vehicle according to claim 5, whereinthe activity signal is transmitted on a CAN bus connection.
 15. Themotor vehicle according to claim 5, wherein at least one of thefollowing is used as activation element: an ignition switch forswitching on the ignition of the vehicle; a vehicle brake operatingelement; a transponder code card.
 16. The motor vehicle according toclaim 5, wherein the clutch control device controls the engagement ofthe clutch prior to deactivation of the clutch control device.
 17. Themotor vehicle according to claim 16, wherein a variable predeterminablelength of time lies between the engagement of the clutch and thedeactivation of the clutch control device.
 18. The motor vehicleaccording to claim 5, wherein the activity signal comprises one of: anactivity signal of the further control device an engine rpm-rate signaln_(mot) a throttle valve signal a fuel injection rate signal an enginetorque signal M_(mot) a wheel rpm-rate signal n_(rad) a transmissionrpm-rate signal n_(trsm).
 19. A method for controlling an automatedclutch in a drive train of a motor vehicle with at least one clutchcontrol device for controlling the automated clutch and a furthercontrol device, wherein said control devices are activated with theoperation of an activation element for switching on and deactivated withan operation for switching off, wherein the method comprises:interrogating whether an ignition signal or an engine rpm-rate signal ispresent at the clutch control device; with the presence of at least oneof the ignition signal and the engine rpm-rate signal, leaving theclutch control device activated; with the absence of the ignition signaland the engine rpm-rate signal, sending no signals from the clutchcontrol device through a data bus; with the absence of the ignitionsignal and the engine rpm-rate signal, deactivating the clutch controldevice.
 20. A method for controlling an automated clutch in a drivetrain of a motor vehicle with at least one clutch control device forcontrolling the automated clutch and a further control device, whereinsaid control devices are activated with the operation of an activationelement for switching on and deactivated with an operation for switchingoff, wherein the method comprises: interrogating whether at least one ofan ignition signal, an engine rpm-rate signal and an engine controlactivity signal exists at the clutch control device; with the presenceof at least one of the ignition signal, the engine rpm-rate signal andthe engine control activity signal, leaving the clutch control deviceactivated; with the absence of the ignition signal and the enginerpm-rate signal or the ignition signal and the engine control activitysignal, sending no signals from the clutch control device through a databus; with the absence of the ignition signal and the engine speed signalor the ignition signal and the engine control activity signal,deactivating the clutch control device.
 21. The method according toclaim 19, wherein prior to deactivation of the clutch control device theclutch is engaged.
 22. The method according to claim 19, wherein awaiting time is observed prior to the deactivation of the controldevice.
 23. The method according to claim 21, wherein a waiting time isobserved prior to the engagement of the clutch.
 24. A motor vehiclehaving a plurality of control devices which are activated by anactivation element sending an ignition signal V_(Z), wherein saidplurality of control devices are in signal connection with each otherand mutually monitor each other, and wherein of said plurality ofcontrol devices at least one control device is not deactivated in theabsence of the ignition signal V_(Z) if the ignition signal V_(Z) ispresent in at least one other control device, or if a signal that isdifferent from the ignition signal but is indicative of the presence ofthe ignition signal is present at the at least one control device.